PURPOSE
A set of tutorial exercises is included to help you get some idea of how this system
works. Just reading about it makes it sound unduly complicated! Try the exercises
in the example pages (above) and you will understand the principles involved.
Provides a comprehensive, general purpose, 2D particle system simulator and renderer. A
variety of natural phenomena can be modelled using this, and many interesting effects can
be achieved. This system is much more flexible than the particle based Monsters in Box 4
and Box 6, though those are to be recommended when you want the particular effects they
were designed to produce.
INPUT CLIPS
Any of the input clips can also be used as an alternative colour source
for the particles.
TIME EDITOR CONTROLS
CREATION
Fecundity Variance (Min: 0.0 Max: 1000.0 Default: 10.0)
LIFE
Variance (Min: 0.0 Max: 100.0 Default: 5.0)
EXTINCTION
Time (Min: 1.0 Max: 1000.0 Default: 50.0)
Variance (Min: 0.0 Max: 1000.0 Default: 20.0)
POSITION
Radius (Min: 0.0 Max: 500.0 Default: 10.0)
FORCES
VELOCITY
Angle (Min: -0.0 Max: 360.0 Default: 90.0)
Scale (Min: -2000.0 Max: 2000.0 Default: 100.0)
Magnification Variable (Min: 0.0 Max: 1000.0 Default: 0.0)
Direction Variance (Min: 0.0 Max : 100.0 Default: 5.0)
GRAVITY
Strength (Min: 0.0 Max: 100.0 Default: 10.0)
Angle (Min: 0.0 Max: 360.0 Default: 270.0)
SWIRL
Density (Min: 0.0 Max: 100.0 Default: 0.0)
Amplitude (Min: 0.0 Max: 100.0 Default: 10.0)
To Maximum (Min: 0.0 Max: 100.0 Default: 5.0)
WIND
XY Source (Default: center left)
XY Target (Default: center right)
Speed (Min: 0.0 Max: 180.0 Default: 0.0)
Spread (Min: 0.0 Max: 180.0 Default: 33.0)
SINK
XY Position (Default: center)
Outer Radius (Min: 0.0 Max: 1000.0 Default: 50.0)
Strength (Min: -500 Max: 500 Default: 0.0)
Swirl (Min: -100.0 Max: 100.0 Default: 3.0)
Hole Radius (Min: 0.0 Max: 100.0 Default: 1.0)
BOUNCE CLIP
TURBULENCE CLIP
Flow Magnitude (Min: -1000.0 Max: 1000.0 Default: 200.0)
Friction (Min: 0.0 Max: 100.0 Default: 0.0)
SIZES
SHAPE
Radius (Min: 1.0 Max: 20.0 Default: 1.0)
Radius Variance (Min: 0.0 Max: 100.0 Default: 0.0)
Streak (Min: 0.1 Max: 1000.0 Default: 100.0)
COLOUR
Colour Variance (Min: 0.0 Max: 100.0 Default: 0.0)
Monochrome Variance (Min: 0.0 Max: 100.0 Default: 0.0)
Source (Default: RGB Values)
DENSITY
Initial (Min: 0.0 Max: 100.0 Default: 100.0)
Condensation (Min: 0.0 Max: 1.0 Default: 1.0)
PI CONTROLS
KILL ALL PARTICLES
STYLE
SELECTING AN IMAGE
self matting (Default: Off)
WIND TYPE
RENDERING STYLE
CLIP CONTROL
bounce (Default: Off)
turbulence (Default: Off)
There are 3 styles of turbulence which control how gradients in the
luminance of the turbulence map images are used to perturb
particle velocities. It is best to experiment with the three possibilities
to see what they do, but in essence:
Birth Clip: if you use birth limits, particles will only be born within
non-black regions of this image.
Bounce Clip: if you use bounce regions, when a particle moves from a black
to a non-black region of this image, its direction will be reflected off the non-black
region edge, making it bounce off the non-black region.
Turbulence Clip: if you use the turbulence map, the gradients in the luminance
of this image will control how the particles move (to some extent). This lets you make
particles flow over features in this image.
Background Clip: sequence over which the particles will be composited.
Fecund ity(Min: 0.0 Max: 10000.0 Default: 50.0)
The average number of particles born per frame.
The actual number of particles born at each frame is the average number specified by
Fecundity plus or minus a random amount ranging up to the specified Fecundity Variance.
Time (Min: 1.0 Max: 1000.0 Default: 50.0)
The average number of frames for which a particle will live. It will definitely be killed
after it has lived this number of frames (plus or minus the lifetime variance
below). They may die sooner (see Extinction).
The actual lifetime of a particle is the average lifetime plus or minus a random number
ranging up to the variance.
These controls determine how particles fade away as they grow older.
The number of frames over which a particles density will fade to zero. If this is very
large compared to the lifetime, the particles will not fade noticeably before they are
killed. Particles that have faded to invisibility are removed. This can cause them to die
before their specified Lifetime is over.
The actual frames to extinction of a given particle is the extinction plus or minus a
random number ranging up to extinction variance frames.
These control where particles are born at each frame.
XY Center (Default: center)
Co-ordinates of the position on which particle birth is centered.
The radius of a circle centered on the particle birth position at each frame.
Particles are born only within this circle.
These control where and how quickly the particles are going when they
are born.
Strength (Min: 0.0 Max: 100.0 Default: 10.0)
The strength determines the speed with which the particles are moving
at birth. The greater the strength, the faster they will move in the given
direction.
The direction the particles move at birth.
Scaling the velocity gives easier and more precise control to the
direction, and change of direction of the particles at birth.
The speed of a given particle can be randomly distributed around the
average velocity (see above) by using this control. This specifies a fraction
of the average speed. The final speed is randomly distributed between the
average speed and the average speed plus or minus this factor times the
average speed.
The direction in which a particle starts travelling when it is born can
be randomly distributed around the average direction (determined from
the velocity direction ) using this control. This gives the maximum
deviation from the average direction as a fraction of a full circle.
At 100.0 particles will burst out in all directions (though with more still
in the average direction), while at 0.0,they will all head off in the same
average direction.
Gravity makes particles accelerate in a specified direction.
Strength of gravity in pixels per frame per frame.
Direction in which gravity acts, specified in degrees, with 0.0 due East. The default is
downwards, which is 270 degrees.
Generally, particles travel through some medium which is not perfectly smooth, such as
air, or water with currents. Often, natural looking results can be obtained by simulating
a turbulent velocity field. These controls set up such a field.
Controls how many bumps in the field the particles will run in to as they cross the frame.
If it is set to 0.0, no swirling will occur. The higher this is, the more detail there
will be in the particles motions.
Controls how much of a kick the particles get when they run into bumps in the field. The
greater this is, the wilder their gyrations will become.
The swirling of a particle builds up from zero when it is born to a maximum (determined by
Swirl Amplitude and Swirl Density) over the number of frames specified here. When the
particle has been alive for this number of frames, it will be as swirl as it will ever be.
Particles can be blown by a directional wind force or a multi directional
wind.
Co-ordinates of where the wind is blowing from. If multi-directional
the wind will blow outwards from this point in all directions. Otherwise
the wind will blow towards the target within the angle specified by the
spread.
Co-ordinates of where the wind is blowing to if the wind is directional.
When the wind is mutli-directional, the wind speed will drop to 0.0 at this
distance from the wind source.
The speed of the wind. Particles feeling the full force of the wind get this velocity (in
pixels per frame) added to their velocity.
Angle of a cone within which the directional wind blows.
The wind speed drops smoothly from wind speed
within the central 90% of the cone angle, to zero at the cone edges.
The particles can be made to fall into a vortex or sink hole. When they come within the
vortex's sphere of influence they will be attracted towards its center and whirled around
its circumference. There is a region at the center of the vortex in which particles are
killed as they enter.
Co-ordinates of the center of the sink hole.
Radius of the sink hole's sphere of influence. Outside this radius, particles are
unaffected. Within it, they are subjected to increasingly strong radial and tangential
forces as they fall towards the center.
Controls the strength of the radial forces in the sink hole, pulling the particles towards
its center. If negative, the sink hole expels particles.
Controls the strength of the tangential forces whirling the particles around the sink
hole. The sign controls whether they are pushed clockwise or anti-clockwise.
Radius of the central region of the sink hole. Any particle that enters this region is
killed (removed from the simulation).
Damping (Min: -2.0 Max: 2.0 Default: 0.1)
When a particle bounces, its new direction is found by reflection. Its new speed is its
incoming speed multiplied by this factor, which determines how bouncy
the particles are.
Direction Magnitude (Min: -1000.0 Max: 1000.0 Default: 100.0)
In Direction mode only, controls how luminance gradients in the turbulence map change the
direction of particles.
Controls the size of a particles reaction to the turbulence map.
A fraction of a particles velocity lost at each frame due to friction. If this is set to
100.0, the particles won't go anywhere. If it is set to zero, they may keep on going (or
accelerate) forever. In between, things like slowing due to air resistance and liquid
viscosity can be simulated.
If the particles are not points or streaks the size of the
particles can be set.
When a lump is used as the particle representation, this specifies its
radius in pixels.
The size of a lump representing a given particle can be made to vary randomly from the
specified lump radius using this control.
When using streak particles, scales the natural length of a streak; the motion
path between 2 frames is drawn.
Red Green Blue (Default: White)
This colour is the basic color that particles are given when they are born. You can
vary this color randomly using the colour variance and mono variance controls.
When particles are born, they are given an initial color as specified.
The red, green and blue components of this color can be randomly perturbed
by plus and minus color variance of the maximum color range. At 0.0, all
particles have the same color. At 100.0, particles
will be born with wildly differing colors.
Specifies the brightness variation of particles without changing their colour.
At 100.0, particles will vary in brightness from black to the luminance
of the color they are given. At 0.0, the only brightness variation will be
that due to any color variation selected.
The colour for the particles can come from either the set RGB values with
the colour and momochrome variances; or one of the input clips can be used
as the colour source. For example, if you want to take the colour from a clip and
are not using the birth region options, then you can select to use this clip
for the colouring instead. Which ever clip you have free, you can use as a
colour source.
RGB=0: the colour for each particle is taken from the RGB values.
Background=1: the color of each particle is take from the background
clip.
Birth=2: the color of each particle is take from the birth clip.
Bounce=3: the color of each particle is take from the bounce clip.
Turbulence=4: the color of each particle is take from the
turbulence clip.
The image is tiled to cater for particles born out side of the image area.
These determine how particles are rendered and control their density when
they are born. Condensation and fading also effect the
density of any given particle on any given frame.
Specifies the maximum density of particles. A density of 0.0 is entirely transparent,
while 100.0 is fully opaque. If condensation is set to 100.0, initial density
gives the density of particles when they are born. They may (and generally will)
fade away as time goes on. If Condensation is less than 100.0, particles
slowly condense into being over a number of frames, heading towards the
density set by initial density. Depending on how
quickly they are set to fade away, they may never reach this density.
This controls how quickly particles gain their maximum opacity after they have been born.
If set to 100.0, they get their full density immediately. At
0.0, they grow in density over their entire lifetime (though they may start
to fade away before they reach their full density). Intermediate values
give intermediate rates of condensation after birth.
Activate to remove all the current particles from memory and start again.
This selects the representation to be used for rendering particles.
point: a single pixel dot.
soft points: each particle contributes a fractional amount of color and density to
the pixel it lies in. This is currently hardwired at 0.25.
streak: an anti-aliased line joining the position of the particle in the previous
frame to its position in the current frame. The density of the line varies from zero at
the old end to whatever the particles current opacity is at the current frame end.
Although the natural length of the streak is from the old to the new position, this can be
scaled by the Streak Scale control.
lump: an anti-aliased blob whose size is determined by the Lump Radius and Lump
Radius Variance controls.
star: a star pattern.
image: an arbitrary image. The image must be in SGI RGB format with a .sgi
extension. We also strongly recommend the use of
small input images (e.g. 100 by 100 pixels as a maximum) since these are generally best
suited for use as particle representations and the larger the image the more memory you
will need and the slower it will be to process.
Tip: use snapshot to grab a small image.
Click on the select button. Use the standard browser to find the
image you require whgich must be SGIRGB format.
When using the image particle representation, this controls how the images,
representing each particle, composite with one another. Try it out
to find which one you fancy.
You can select the wind type, a cone of directional wind is the default.
Determines how particle representations fade with time. The rate at which
they fade is controlled by the Extinction and related controls.
colour & density: the color (brightness) of a particle and its density
(opacity) change as it gets older.
colour: the color (brightness) of a particle changes, while its
density stays constant.
density: the color (brightness) of a particle stays constant, while
its density (opacity) changes as it gets older.
This control effects how the particles composite with one another and with
the background image. It has a very great effect on the final appearance of the
rendered particles.
birth (Default: Off)
On: particles will only be born in the intersection of the birth
circle and non-black regions of the images in the birth matte clip.
On: particles will be bounced when they move from black to non-black regions of the
bounce zone image. A 2D analog of a normal is calculated from the bounce zone image and
particles are reflected off the surface.
Often, its cool if particles can react to elements in a background image. For example, you
might want to simulate water with a particle system and have it bounce off rocks. You can
do this with a bounce zone clip. Particles can (and generally will) bounce
more than once.
On: another velocity perturbation field will be used in addition to the
turbulent velocity field. This is controlled by the luminance of
the turbulence map clip.
attraction: draws the particles towards light (or dark) areas of the
turbulence map. Particles can become stuck to the map. The force of attraction
is controlled by flow magnitude, the sign of which determines whether light
or dark areas do the attracting.
direction: makes the particles change direction as they hit gradients
in the luminance of the turbulence map. Flow magnitude controls the extent
to which they change direction. Direction Magnitude changes which direction
they go in as they move from, for example, light to dark.
accumulation: similar to attraction, but particles don't become stuck.